The discomforting angle: After busting unscrupulous parts suppliers Friday, investigators have no way of pinpointing aircraft flying with equipment that could fail. They say that all they do is issue warning bulletins to the airline industry and hope mechanics detect defective parts.

"The onus is on the buyer," said Harry Schaefer, an assistant chief inspector for the U.S. Department of Transportation. "A parts distributor has no obligation to keep track of where equipment was sold. By the time the parts pass through two or three middlemen, you lose all traceability."

To date, no evidence has been uncovered that Miami's burgeoning black market in aircraft parts has resulted in injury or accidents. But federal investigators fear that it's a matter of time and have launched a nationwide crackdown in hopes of avoiding a disaster.

"The issue is safety," said Paul Philip, head of the FBI's Miami office. "We all fly too much to allow these parts to be used."

The method is simple: Salvaged or stolen parts are sold with bogus Federal Aviation Administration inspection tags certifying that they have been overhauled. But the work was never done.